How to: Retain the Image URI in HTML Document

This example describes HTML export in more detail and provides a solution on how to store the original image URI in the exported document.

When RichEditControl loads an HTML document, it performs HTML import and transforms the document into a native document model. When RichEditControl saves a document, it performs a document export from the native format to the resulting document's format.

When saving a document as HTML, there are two options for saving images, described in the table.

Save images as separate files. The images are named with the "image" word followed by its sequential number in a file. Images are saved to the folder with the name that is the combination of the file name, underscore and the "files" word. That is, the first png image in the resulting Test.html file is saved to the Test_files\image0.png location.

HTML

<img src="test_files/image0.png" alt="" style="border-width:0px;" />

Different methods produce different results, as shown in the following table.

The HtmlDocumentExporterOptions.EmbedImages property accessible using the RichEditControl.ExportOptions.HtmlOptions.EmbedImages notation determines whether images are embedded or saved as separate files.

The HTML exporter uses an URI provider instance to obtain the URI string for each image. There are several built-in URI providers - the FileBasedUriProvider which provides image file names and the DataStringUriProvider that constructs a tag for embedded base64 data. The built-in URI provider service (a service that implements the IUriProviderService interface) is used to obtain a provider instance of a proper type.

You can implement a custom URI provider to specify a custom location for each image when the document is saved to an HTML format. To accomplish this, create a IUriProvider descendant and register it in RichEditControl services.

Tip

The SubDocument.GetHtmlText method allows you to specify a custom URI provider as the method's parameter, bypassing the URI provider service and the RichEditControl.ExportOptions.HtmlOptions.EmbedImages option.

Each image in RichEditControl has the OfficeImage.Uri property that is the original image URI. To save an original image URI to the exported HTML document, our custom UriProvider returns the OfficeImage.Uri value.